1. Field of the Invention
The present invention relates to a magnetic memory medium to be applied to a hard disc drive and a method of manufacturing the same medium.
In recent years, a hard disc drive playing the centric role of an information memory apparatus is requested to assure reduction in size and enhancement in the storage capacity. These requests can be realized with improvement in the surface recording density of a magnetic disc medium. The surface recording density includes the line recording density in the circumference direction of the disc medium and the track density in the radius direction thereof. Therefore, higher surface recording density can be attained with improvement in any one density or both densities explained above. The present invention particularly relates to the technique to contribute to improvement in the track density.
2. Description of the Related Art
In the related art technique, there is provided a magnetic disc medium 60 by forming an underlayer film 3 with formation, as illustrated in FIG. 1(a), of a chromium layer on a non-magnetic substrate 2 such as aluminum substrate, forming a magnetic film 4 consisting of an alloy mainly composed of cobalt on the underlayer film 3 and also forming a protection film 6 such as amorphous carbon on the magnetic film 4.
In order to enhance track density of a magnetic disc medium, it is necessary to reduce the recording track width by narrowing the core width of a recording magnetic head. However, in the system utilizing a magnetic head for recording of information, extra-recording is conducted to the region (guard band) between the recording tracks with a leakage field generated from the side surface of the recording head. Such extra-recorded region is called the side erase which will become a cause of noise during the reproducing operation. Moreover, even when the core width of the recording magnetic head is narrowed by improving track density, since the width of side erase does not particularly change if the gap length and head flotation amount are not reduced, it is difficult, due to reduction of track width, to acquire the S/N ratio while reproducing the recorded data.
Therefore, as illustrated in FIG. 1(b), there is proposed a disc medium 61 wherein a groove 9 is previously formed along the circumferential direction of a disc substrate 2 and then it is used as a guard band to physically isolate the track. The magnetic disc medium 61 is considered very effective for realizing higher density of the track because the track edge noise can be controlled when the groove has sufficient depth.
However, on the medium on which the groove is formed, an uneven surface having a level difference of several tens of nm to several hundreds of nm is finally left on the surface. When considering the future trend of the magnetic disc medium indicating that the flotation of the magnetic head becomes 30 nm or less with enhancement of density of the magnetic disc medium, a problem of reliability will occur due to the reason explained below.
In the hard disc drive, high speed revolution of disc generates air flow to float a slider mounting a magnetic head and thereby the magnetic head executes the data recording and reproducing operations through non-contact with the disc. However, it is known that if the disc has an uneven surface, the flotation amount of the slider varies to become unstable depending on disturbance of an air flow. This fact has been neglected when the flotation amount is comparatively as large as 50 nm to 100 nm, but it becomes a major problem when the flotation of slider is as small as 30 nm or less which will be required in the future.
Therefore, an object of the present invention is to provide a magnetic recording medium which assures higher recording density.
Moreover, another of object of the present invention is to reduce the track edge noise of the magnetic recording medium.
In addition, the other object of the present invention is to realize stable floating of a magnetic head.
In the magnetic recording medium of the present invention, groove and land are formed on a substrate and a magnetic film is laminated on this substrate. Therefore, tracks are magnetically isolated to reduce the track edge noise. Moreover, on the magnetic film on the groove, a non-magnetic material is deposited up to a position higher than the land surface on the substrate. According to this structure, a level difference resulting from the land and groove of the substrate is reduced at the surface of the medium and thereby the medium surface becomes almost flat. Therefore, the air flow generated by revolution of the medium is never disturbed and thereby stable floating of the magnetic head for recording or reproducing information to or from the magnetic recording medium can be assured.
Moreover, in the present invention, after a magnetic film and a non-magnetic film are sequentially laminated on the substrate on which groove and land are formed, a non-magnetic film is fused through the heat process. Thereby, a non-magnetic material fuses on the groove to deposit a non-magnetic material on the groove. As a result, level difference between the groove and land is reduced on the medium surface to attain flatness of the medium surface. Here, the problem that the other materials are also fused when the non-magnetic material is heated can be eliminated by introducing, as the material of non-magnetic film, a material having the melting point lower than that of the other materials forming the magnetic recording medium. Moreover, when a non-magnetic material film laminated on the land is fused and thereby eliminated from the land, the groove is perfectly filled with the non-magnetic material film and a flat surface of the medium can be attained without leaving extra non-magnetic film on the land by laminating the non-magnetic film in the depth of groove width/land widthxc3x97groove depth.